Greece's beleaguered government, which as been buffeted by a barrage of strikes, faces one of its toughest tests yet as it prepares to pass reforms seen as pivotal to the country's economic recovery.

Ahead of Friday's crucial EU summit, George Papandreou, the prime minister, has come under increasing pressure from unions and the professions. Both groups are vowing to step up their protests against the unprecedented efforts to liberalise the economy.

Dimitris Reppas, the transport minister, appealed for calm and said striking employees would feel the "full force of the state" if they did not return to work. "We all have to give up something so that Greece comes out on top," he said.But the crippling action shows no sign of letting up even as EU and International Monetary Fund officials grill Athens over the progress it has made in adopting policies demanded in return for their €110bn (£95bn) bailout of the country last year.

A week after the socialist government presented draft legislation aimed at opening up some 150 "closed-shop" occupations – a key condition of the emergency aid – public transport workers, pharmacists, civil engineers, doctors and lawyers have all walked off the job citing loss of hard-won rights. Sweeping away the laws that have kept Greek labour costs artificially high, protected professions and contributed to the nation's lack of competitiveness is essential to resuscitating an economy teetering on bankruptcy.

One thinktank in Athens estimated that Greece's GDP would increase by more than 12% once the economy is reformed. The country's international creditors have signalled that unless the reforms are passed, it risks losing the next instalment of aid.

The government has been caught off guard by the scale of resistance. Since inheriting the debt crisis 16 months ago, it has won praise abroad, pursuing austerity measures that have helped cut the budget deficit by a record 6%, but in so doing has become increasingly unpopular at home. "There is a sense … that somehow we are off-message, because Greeks don't seem to understand that we are doing this to save the country," said one senior government official.

In recent weeks there has been a growing movement of civil disobedience with people refusing to pay road tolls, hospital fees and public transport costs which, on Tuesday, increased by as much as 40%.

"Reppas claims he is justified in making these unacceptable hikes because Athens continues to have some of the lowest costs, but he fails to say that we also have some of the lowest wages," said Lia Frangou, who has enlisted with a group called the Open Committee of Passengers, whose members refuse to pay for public transport.

Passage of the reforms, which also include streamlining state-run companies, cuts to the health care system and an overhaul of the tax system, are also seen as vital to the EU and IMF agreeing to a "backdoor" restructuring of Greece's €330bn debt.